Several species of mammalian C-type viruses contain internal proteins which share antigenic determinants with proteins from other species of mammalian C-type viruses. The viral polypeptides which contain these common determinants are available in highly purified and immunologically active forms. These common interspecies components, as well as species-specific components, have been isolated from murine, feline and subprimate leukemia viruses, and antisera specific to each separate component have been prepared. Human benign and malignant bladder tissues will be examined for either the presence of whole oncogenic C-type viruses or the expression of their genetic material by reacting extracts of the tissues with the feline and murine and sub-primate C-type interspecies antisera. Malignant and benign bladder tissue obtained from surgery will also be established in tissue culture. Sera of patients with histologically established benign and malignant bladder disease, collected before and after therapeutic manipulation, will be used in conjunction with viral reagents in competition radioimmunoassays to determine possible reactions with antiviral sera. Patient sera will be used directly to determine (a) possible mass reactivity with viral interspecies components, and (b) cytotoxic effects on cells from benign and malignant bladder tissue already established in tissue culture. Patient lymphocytes will be obtained both before and after surgery and incubated with bladder tumor membrane preparations in short-term tissue culture to determine the ability of the membranes to stimulate the patient lymphocytes as an index of the immunologic status of the therapeutically manipulated tumor host. Tumor homogenates which react with interspecies antisera will be analyzed so that the reacting proteins may be characterized as to molecular weight and biochemical properties, and reagent materials will be sought which may identify the clinical status of the patient.